The purpose of this project is to obtain knowledge about the physiological role of 2-hydroxyestrogens in the regulation of gonadotropin and prolactin secretion. Two lines of investgation will be followed. One of these is concerned with the specific estrogen-2-hydroxylase found in the rat brain and pituitary. We plan to study the nature and localization of this enzyme in the CNS, and changes in its activity during the estrus cycle and under the influence of exogenous steroids and opiate agnosts and antagonists. Inhibitors of this enzyme will be sought and their biological effects examined in vivo in the context of the hypothesis that the formation of the 2-hydroxyestrogens in the CNS is the critical element in their function. Antisera to 2-hydroxyestrogens will be administered intracerebrally and their effects on piturary secretion assessed to see whether results similar to those with the enzyme inhibitors are obtained. The other line of investigation is concerned with effects on pituitary function by exogenous 2-hydroxyestrogens in the rat and in the human. Cycling rats equipped with artrial cannulae will be treated with 2-hydroxyestrone at various times on proestrus to assess its action on the preovulatory surge of gonadotropin and prolactin. The estrogen primed oophorectomized rate model will also be used to see whether administration of 2-hydroxyestrone affects the cyclic pituitary secretion on the subsequent day. Infusion of 2-hydroxyestrone to human volunteers will be carried out to confirm and expand previous results on its prolactin suppressing properties. The action of this material on tonic and preovulatory secretion lf LH, FSH will be studied. The combined results of the laboratory, animal, and human studies should provide the essential linformation about the physiological role of the 2-hydroxyestrogen.